In recent years one has become increasingly aware of the impact of human activities on the environment and the negative consequences this may have. Ways to reduce, reuse and recycle resources are becoming more important. In particular, clean water is becoming a scarce commodity. Therefore, various methods and devices for purifying water have been published.
A method for water purification is by capacitive deionisation, using an apparatus provided with a flow through capacitor (FTC) to remove ions in water. The FTC functions as an electrically regenerable cell for capacitive deionisation. By charging electrodes, ions are removed from an electrolyte and are held in electric double layers at the electrodes. The electrodes may be charged with a voltage between 0.5 to 2 Volts. The electrodes may be (partially) electrically regenerated to desorb such previously removed ions without adding chemicals.
The apparatus to remove comprises one or more pairs of spaced apart electrodes (a cathode and an anode) and a spacer, separating the electrodes and allowing water to flow between the electrodes. The electrodes are provided with current collectors or backing layers that are generally adjacent to or very near the electrodes and a material to store the ions. Current collectors are electrically conductive and transport charge in and out of the electrodes.
The apparatus may comprise a housing comprising an inlet to let water into the housing and an outlet to let water out of the housing. In the housing, the layers of electrodes and spacers are stacked in a “sandwich” fashion by compressive force, normally by mechanical fastening.